SelectBeckley Airport

Springfield, Ohio 45502

937-398-0313

SelectTech GeoSpatial

EH-4 VTOL Technical Manual

Rev: 1.9

Date: 17 March 2015 

SelectTech GeoSpatial LLC

Springfield Beckley Airport

Springfield, Ohio 45502

937-398-0313
EH-4 Technical Manual

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Contents

I. Introduction ..........................................................................................................................................3

II. sUAS Basics............................................................................................................................................4

III. Components......................................................................................................................................5

Airframe ....................................................................................................................................................5

Power and Control System .......................................................................................................................6

Motors and Electronic Speed Controllers.................................................................................................8

Propeller Assembly ...................................................................................................................................9

Controls...................................................................................................................................................10

Primary Radios........................................................................................................................................12

Telemetry................................................................................................................................................14

Autopilot.................................................................................................................................................14

IV. VTOL Flight Characteristics .............................................................................................................17

Manual Controls......................................................................................................................................18

Telemetric Controls.................................................................................................................................19

Autopilot Flight Modes...........................................................................................................................20

V. Flight Safety.........................................................................................................................................24

General Flight Safety Guidelines.............................................................................................................24

Spotters:..............................................................................................................................................24

Operating Parameters.............................................................................................................................24

General Preflight Checklist......................................................................................................................25

VI. Available Sensor Packages..............................................................................................................27

VII. Maintenance ...................................................................................................................................28

Recommended Spare Components........................................................................................................28

Aircraft Maintenance..............................................................................................................................29

Batteries and Safe Charging....................................................................................................................30

Battery Maintenance ..............................................................................................................................32

 Civil UAS ......................................................................................................................................34

 Public UAS ...................................................................................................................................34

 Model Aircraft.............................................................................................................................34
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Table of Figures

Figure 1 EH-4 Airframe..................................................................................................................................5

Figure 2 EH-4 Block Diagram.........................................................................................................................6

Figure 3 EH-4 Motor......................................................................................................................................8

Figure 4: Propeller / Motor Assembly...........................................................................................................9

Figure 5: Propeller Orientation / Motor Rotation ........................................................................................9

Figure 6: Control Signal Diagram ................................................................................................................10

Figure 7: Spectrum Satellite Receiver.........................................................................................................12

Figure 8: Spektrum DX8 Transmitter ..........................................................................................................13

Figure 9:3D Robotics Telemetry Transceiver..............................................................................................14

Figure 10: Pixhawk Autopilot......................................................................................................................15

Figure 11: Command and Sensor Inputs.....................................................................................................16

Figure 12 Spektrum DX8 Transmitter .........................................................................................................18

Figure 13 Rotational rate is proportional to stick angle. ............................................................................19

Figure 14 Sensor Cassettes available for the EH-4......................................................................................27

Figure 15 Typical Propeller Balancer...........................................................................................................30

Figure 16 Battery Analyzer..........................................................................................................................32

Figure 17 Battery Charger...........................................................................................................................33
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I. Introduction

Thank you for purchasing the EH-4 VTOL (Vertical Take-off and Landing) small 

Unmanned Aerial System (sUAS). The EH-4 is specifically designed for heavy duty industrial, 

public service and agricultural applications. The airframe is constructed from fiberglass 

reinforced polyester resin and high impact engineered thermoplastic and can resist rough 

landings and challenging environments. This aircraft is also designed for ease of assembly / 

disassembly aiding in quick repairs and modifications. This operations manual will cover 

significant maintenance and flight operations details. Additional references are added for 

context and deeper understanding of the technology relating to this aircraft.

Safety

Aircraft safety should to be constantly in the forefront of the pilot in charge (PIC) Observer 

and all other mission participants. The EH-4 is a serious aircraft that is designed for heavy-duty 

applications. The EH-4 is not designed nor recommended for recreational use. This aircraft uses very 

powerful Lithium Ion batteries that can seriously burn the operator if used improperly. The 

propellers on this aircraft and very sharp and when rotating can present a serious hazard. 

The same precaution used with full scale aircraft need to be observed. Many fail-safe 

systems are included with this aircraft however, when not properly used this aircraft can be a 

dangerous projectile. This aircraft is also capable of flying in restricted airspace. As with and any 

aircraft, all precautions need to be taken to avoid interference with other aircraft. Thought this 

operations manual, safety items will be emphasized and bordered in yellow.
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II. sUAS Basics

sUAS used today fall into 3 main configuration categories:

 Fixed Wing

 Helicopter

 VTOL

There is no coincidence that the configuration categories look very similar to their fullscale counterpoints. All sUAS designs borrowed from previously existing airframes. VTOL’s 

(Quads, Hexes etc.) are newer designs that exist because of developments in motors, batteries 

and sensor miniaturization. 

This manual is dedicated to the EH-4 VTOL operations, maintenance and related accessories.

There are numerous benefits of sUAS operations that can mitigate safety concerns of manned 

flight operations, manned ground operations, and added benefits unique to sUAS. Aside from 

the weight, speed, altitude, and operating perimeters offered by sUAS, the most important 

safety aspect is that sUAS are unmanned, greatly reducing loss-of-life and serious injury risks. 

sUAS grant the user the ability to move closer to equipment without causing harm to either the 

structure being inspected or the personnel on the ground. Maneuverability allows for data 

output unseen in many industries.
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III. Components

The ability for the EH-4 VTOL to launch and remain airborne relies on a number of systems and 

subsystems that must operate in concert. A short list of these systems includes:

 Airframe

 Power and Control System

 Motors

 Propeller Assembly

 Controls

 Primary Radios

 Autopilot

 Telemetry Radios

Airframe

The airframe of the EH-4 consists of a Top Plate, Bottom Plate, Legs, Canopy and 

fasteners. The top plate, bottom plate and legs are made from G-10 fiberglass 

composite and the canopy is made from high impact resistant Kydex® engineered 

thermoplastic. The airframe provides the basic structural members of the aircraft.

Figure 1 EH-4 Airframe
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Power and Control System

The power system provides electrical energy for the motors as well as all of the flight controls. 

It consists of a Lithium Ion Polymer (LiPo) battery, polarized connectors, distribution harness 

and battery monitor. The battery requires special charging equipment as well as proper care to 

maintain the battery’s energy density. As with all LiPo batteries, special precautions need to be 

in place as they can deliver high instantaneous currents. Additional information on battery 

safety and maintenance is provided in Chapter IX.

Pilot control inputs sent from the transmitter to the receiver are combined with onboard sensor 

outputs by the autopilot (AP). The AP generates speed control signals for the ESCs so the 

motors maintain a stable flight platform.

Two-way radio telemetry provides for additional aircraft control, mission parameters and 

feedback to the pilot about aircraft position, battery capacity, sensor health, etc.

Figure 2 EH-4 Block Diagram
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(a) Battery: A Lithium Ion battery, completely modular to allow for rapid 

battery changes between missions.

(b) Power connector/distributor: Provides power through polarized connectors

to components of the aircraft including the autopilot, radios and 

ESCs/motors.

(c) Battery power indicator: Equipped with a visual indicator of battery health 

as well as a speaker for warning alerts.

(d) Electronic Speed Controller (ESC): Receives information from the AP and 

converts it into a three-phase control signal. This three-phase signal drives 

the brushless motor to attain a specific number of revolutions per minute.

(e) Motor: Four motors and propellers, M1 and M2 rotate counter clockwise 

and M3 and M4 clockwise. 

(f) Autopilot: The EH-4 utilizes the Pixhawk autopilot (AP) by 3DRobotics. The 

primary function of the Pixhawk is to monitor the orientation of the aircraft 

and drive the multiple motors to achieve stable flight.

(g) Motor Safety Switch (Red): Quick, constant blinking: performing system 

check, Please wait. Intermittent blinking: system ready. Press the safety 

button to activate. Solid: ready to arm. Proceed to the arming procedure.

(h) Telemetry: This two-way radio system provides a secondary method of 

controlling the aircraft, including flight path programming from a PC or 

tablet. Transmitting at 915 MHz it also transmits aircraft performance and 

position data to the ground station.

(i) Receiver: Sends the pilots control inputs (the sticks) to the AP.

(j) Buzzer: Provides audio signals to indicate the arming status of the AP.

(k) GPS/Compass: Determines the orientation of the aircraft with gyroscopes 

and a magnetometer. This data is interpreted by the autopilot and 

adjustments are made to ensure accuracy for transmitter and telemetry 

based controls.

(l) Transmitter: Sends the pilots control inputs (the sticks) to the receiver 

onboard the aircraft to control the roll, pitch, yaw, and altitude of the EH-4. 

(m) Ground Control and Telemetry: This can be a Windows PC, 

iOS/Android/Windows based Tablet, or other optional supported devices

provided by the manufacturer that can collect data from the aircraft during 

flight, including altimeter readings, GPS location, battery life, and other 

important data.
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Motors and Electronic Speed Controllers

The function of the ESCs is to take information from the autopilot and turn it into a 3-phase 

control signal. This 3-phase signal drives the brushless motors to attain a rotational speed to a 

certain number of revolutions per minute (RPM). Full battery power from the power system is 

connected to the input of the ESC as well as the signal output from the autopilot. The three 

phase ESC output wires connect to the three phase wires on the motor. Motor speed is a direct 

function of information from the autopilot system.

The brushless motors on the EH-4 are outrunner style. Outrunner motors are 3 phase motors 

with the rotating section on the outside of the motor. The rotor is lined with powerful magnets 

and the stator a wire-wound pole set with the winding count corresponding to the magnet 

count. The motors are controlled and driven via an electronic speed control (ESC). The ESC 

capacity is matched to the maximum power draw of the motor at full load.

The EH-4 has a motor on each arm.

Figure 3 EH-4 Motor
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Propeller Assembly

The propeller translates motor speed and torque to lift. The propellers provided with the EH-4 

are matched to the weight and payload of the aircraft. Length, pitch and speed are critical for 

maximum performance. Changing the propeller size may adversely affect flight characteristics 

and duration. Also part of the propeller assembly is the hub, washer and retaining nut. These 

items are precisely sized to the propeller and need to remain tight at all times.

To avoid excessive vibration, the propellers must be balanced before installation. Should a nick 

or chip occur on a propeller, it must be replaced prior to the next flight. Most importantly each 

propeller should be inspected for damage and the retaining nut inspected for tightness before 

each mission.

Figure 4: Propeller / Motor Assembly

Figure 5: Propeller Orientation / Motor Rotation
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Controls

The controls of the EH-4 include: primary radios, telemetry radios, and autopilot. The primary 

radio operates in the 2.4 MHz band and uses spread-spectrum modulation to minimize 

interference. The primary radio transmitter provides pilot command signals that give flight

instructions to the aircraft. The primary radio receiver onboard the aircraft receives and 

decodes the signals into flight commands. These commands are sent to the autopilot for mixing 

with data from the onboard sensors. In combination, the resultant control signals are fed to the 

ESCs as commands to each motor.

Both ground and aircraft radios have antennas that should not be blocked or interfered with 

during flight operations. Before every flight, the radio system should be checked for reliable

connection of key maneuvers close to ground as outlined in the preflight checklist.

Figure 6: Control Signal Diagram
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(a) The pilot sends attitude commands to the aircraft using the transmitter. In this example, 

she will send controls to thrust all motors resulting in an upward climb.

(b) The receiver collects pilot commands from the transmitter and pushes it to the 

autopilot.

(c) Simultaneously, the ground station telemetry control sends commands to the aircraft 

via telemetry. Many variables can be used to control the aircraft, including remaining 

battery life, return-to-home failsafe conditions, geofencing, and any other parameters 

monitored by the AP. In this example, the computer directs the aircraft to stop climbing 

after reaching 400’ above ground level (AGL).

(d) The telemetry continually monitors the onboard altimeter/GPS for altitude information. 

(e) If the aircraft exceeds 400’ AGL, the AP will hold the aircraft at the set maximum altitude 

of 400’ AGL.

(f) Data about the health, performance and position of the aircraft are sent to the ground 

station. 

(g) The autopilot sensor data are collected and analyzed. The resulting commands for 

power needed are sent to the ESCs to control the individual motor speeds.

(h) In this example, the aircraft attempted to rise above 400’ AGL so the autopilot 

prevented the EH-4 from continuing to climb by overriding the primary radio

The system of controls for the UAS is very complicated. The above example takes place every 

20 milliseconds from a multitude of components, all at the same time. The preflight 

procedures requires the PIC to set safety parameters for the UAS, and therefore manual 

controls may be overridden; it is the duty of the PIC to be in control of the UAS, which means 

the PIC must understand all autonomous controls set during the preflight procedures. 

For example, if the gyroscope is set to send commands to the motors to account for level 

hovering near ground and the PIC fails to disengage before picking up the UAS, the gyroscope 

will detect the movement, switch on the motors, and cause injury/harm to the person picking 

up the UAS. Always be conscious of the manual and autonomous controls, failsafes, and safety 

procedures.
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Primary Radios

The Primary Radios, also considered the main flight radios, are a pair of SpectrumTM radios. The 

pilot uses the DX8 transmitter to command the aircraft. The SPM9645 PPM sum receiver

communicates those commands directly to the AP. 

Spektrum systems are distinguished in that they use direct-sequence spread spectrum (DSSS) 

technology on the 2.4 GHz ISM band. Spektrum refers to their technology as "Digital Spectrum 

Modulation." Each transmitter has a globally unique identifier (GUID), to which receivers are

bound, ensuring that no transmitter will interfere with other nearby systems. This works in a 

manner that both transmitter and receiver are constantly changing through the different 

frequencies of the 2.4 GHz range. The Spektrum system is also unique in that it offers "Model 

Match" in which each transmitter program for a particular flight model is bound to one and 

only one receiver. The AR8000 supplied with the DX8 has a satellite receiver that is connected 

directly to the Pixhawk autopilot. The SPM9645 is bound to a Spektrum AR8000 to provide 

unique receiver identification. The AR8000 is not installed on the EH-4. It is used solely to bind 

the SPM9645 to a specific radio control transmitter.

Figure 7: Spectrum Satellite Receiver

The switches on the DX8 transmitter are programmed to provide specific instructions to the 

aircraft simply by changing a switch position. A three position switch commands the AP to enter 

one of three operating modes. A two position switch commands the AP to begin a sequence of 

pre-programmed maneuvers. A different two position switch commands the AP to return the 

aircraft to the initial take off location as an added failsafe.
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Figure 8: Spektrum DX8 Transmitter
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Telemetry

Telemetry (Data in both directions) is provided by a 915MHz 3DR radio set. The radio uses 

Frequency Hopping Spread Spectrum (FHSS) modulation and can broadcast a number of data 

channels between air and ground operations. The power output can be set by the main flight 

control system. The unit connects to the AP via a serial connection and ground via a 915 

antenna. More can be found online: http://store.3drobotics.com/products/3dr-radio

Figure 9:3D Robotics Telemetry Transceiver

Autopilot

The primary function of the Pixhawk autopilot (AP) is to monitor the orientation of the aircraft 

and drive the multiple motors to achieve stable flight. The user’s control inputs are then used to 

adjust the aircraft away from a stable orientation by pitching, rolling and yawing (spinning) the 

EH-4. These actions cause the aircraft to move in different directions so that it can effectively 

be flown. To achieve stable flight, data from a magnetometer, gyroscopes, accelerometers, GPS 

and a pressure sensor are fused together thousands of times a second. This information is then 

used to make decisions on how to achieve the pilot’s desired orientation.

The Pixhawk autopilot (AP) is an open source product manufactured by 3D Robotics. Core 

features include a real-time operating system, powerful processor, integration of sensors and 

other sensor technology, multithreading, a fully programmable environment for flexibility in 

creating behaviors and missions, precise timing between components, and a large community 

of developers to allow for expanded capability.

The Pixhawk System includes:

 Pixhawk autopilot

 Audio Warning System

 Safety – Arming Switch

 3DR power module with XT60 connectors and 6-position connector cable

 Extra 6-position cable to connect a 3DR GPS+Compass module

 Standard micro USB cable

 SD card and adapter
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 I2C splitter module with cable

Autopilot Features:

 Advanced 32 bit ARM Cortex® M4 Processor running NuttX RTOS, an open-source 

operating system used for real time microcontroller environments

 14 PWM/servo outputs (8 with failsafe and manual override, 6 auxiliary, high-power 

compatible)

 A multitude of connectivity options

 Built-in fail safes for manual overriding, mixing of manual and autopilot, and dedicated 

processing and power

 Redundant inputs for power

 User-friendly safety controls

 LED indicator 

 Audio warning signal

 Long-time, fast logging of flights onboard with microSD input

Figure 10: Pixhawk Autopilot

Additional information on the Pixhawk AP can be found online at: 

https://store.3drobotics.com/products/3dr-pixhawk.
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Figure 11: Command and Sensor Inputs
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IV. VTOL Flight Characteristics

In order for a VTOL to fly, lift and balance must be created via the onboard motors. To fly in a 

stable hover, the lift at each motor has to be precisely balanced taking into account the 

surrounding environment. Because of the number of variables associated with VTOL flight, an 

autopilot becomes critical in keeping the aircraft balanced and in flight. Using a number

gyroscopes and accelerometers in the pitch, roll and yaw axes along with ground control input, 

the aircraft can maintain controlled flight.

Lift and flight are created with large, balanced propellers mounted on each motor. The 

propellers rotate at high speed delicately controlled via individual electronic speed controls 

(ESC). 

Pitch movement and resultant forward motion is achieved by minutely slowing the front 

motors and speeding up the rear motors. 

Figure 12: Force Diagram
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In order to maintain flight stability and execute the mission, the autopilot receives its 

commands from a number of sources (see figure 10):

 Primary Radio Transmitter 

 Secondary Radio (Telemetry)

 Internal Sensors

 On board memory

Manual Controls

The primary radio sends flight commands that principally control Yaw, Pitch, Rill and Throttle. 

Additional commands may also be managed by the primary radio. Proportional control inputs 

are accomplished via two joy stick controls. The control transmitter is configured in what is 

known as mode 2. Mode 2 has the throttle and yaw on the left stick and the pitch and roll on 

the right stick as seen in figure 11.

Figure 12 Spektrum DX8 Transmitter
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Figure 13 Rotational rate is proportional to stick angle.

Telemetric Controls

The secondary radio (telemetry) is used for sending aircraft parameters to the ground control 

station and can also be used as a flight controller as described above. Commands are sent via 

the ground control station transceiver. The secondary radio is also used to upload mission 

parameters into the on board autopilot memory.

An array of internal sensors are incorporated into the autopilot. These sensors detect and 

measure the aircraft altitude and adjust the flight characteristics according to their inputs in 

concert with programmed algorithms. The installed sensors include:

 Yaw, Pitch and Roll Gyroscopes

 Yaw, Pitch and Roll Magnetometers

 Yaw, Pitch and Roll Accelerometers

 Magnetic Compass

 GPS receiver

 Barometric Altimeter

On board memory of mission parameters also dictates flight parameters and resultant modes. 

Activating the flight mode memory is preformed manually via the primary ground radio. 

Commands from memory can be overridden via the primary ground radio.
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Autopilot Flight Modes

The following flight modes are factory configured on the EH-4. For detailed information on 

flight modes, please go to http://copter.ardupilot.com/wiki/flight-modes/.

Stabilize Mode (manual)

• Pilot’s roll and pitch input control the lean angle of the UAV. When the pilot releases 

the roll and pitch sticks the vehicle automatically levels itself.

• Pilot will need to regularly input roll and pitch commands to keep the vehicle in place as 

it is pushed around by the wind.

• Pilot’s yaw input controls the rate of change of the heading. When the pilot releases the 

yaw stick the vehicle will maintain its current heading.

• Pilot’s throttle input controls the average motor speed meaning that constant 

adjustment of the throttle is required to maintain altitude. If the pilot puts the throttle 

completely down the motors will go to their minimum rate (MOT_SPIN_ARMED) and if the 

vehicle is flying it will lose attitude control and tumble.

• The throttle sent to the motors is automatically adjusted based on the tilt angle of the 

vehicle (i.e. increased as the vehicle tilts over more) to reduce the compensation the pilot must 

do as the vehicle’s attitude changes.

Altitude Hold Mode (Alt Hold)

When altitude hold mode (aka AltHold) is selected, the throttle is automatically controlled to 

maintain the current altitude. Roll, Pitch and yaw operate the same as in Stabilize mode 

meaning that the pilot directly controls the roll and pitch lean angles and the heading.

Automatic altitude hold is a feature of many other flight modes (Loiter) so the information here 

pertains to those modes as well.

Note: The flight controller uses a barometer which measures air pressure as the primary means 

for determining altitude (“Pressure Altitude”) and if the air pressure is changing in your flight 

area due to extreme weather, the copter will follow the air pressure change rather than actual 

altitude.

The pilot can control the climb or descent rate of the vehicle with the throttle stick.

• If the throttle stick is in the middle (~40% - 60%) the vehicle will maintain the current 

altitude.

• Outside of the mid-throttle deadzone (i.e. below 40% or above 60%) the vehicle will 

descend or climb depending upon the deflection of the stick. When the stick is completely 

down the copter will descend at 2.5m/s and if at the very top it will climb by 2.5m/s. 
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Loiter Mode

Loiter Mode automatically attempts to maintain the current location, heading and altitude. The 

pilot may fly the copter in Loiter mode as if it were in manual. Releasing the sticks will continue 

to hold position.

Good GPS position, low magnetic interference on the compass and low vibrations are all 

important in achieving good loiter performance.

The pilot can control the copter’s position with the control sticks.

• Horizontal location can be adjusted with the Roll and Pitch control sticks with the 

default maximum horizontal speed being 5m/s. When the pilot releases the sticks the copter 

will slow to a stop.

• Altitude can be controlled with the Throttle control stick just as in AltHold mode

• The heading can be set with the Yaw control stick.

Return to Launch (RTL)

Return To Launch is a switch selection on a factory configured primary radio as shown in figure 

8.

RTL is a GPS-dependent move, so it is essential that GPS lock is acquired before attempting to 

use this mode. Before arming, ensure that the APM’s blue LED is solid and not blinking. For the 

GPS+Compass module, the LED will be blinking blue when GPS is locked.

RTL will command the copter to return to the home position, meaning that it will return to the 

location where it was armed. Therefore, the home position is always supposed to be your 

copter’s actual GPS takeoff location, unobstructed and away from people. If you get GPS lock 

and then ARM the EH-4, the home position is the location the EH-4 was in when it was armed. 

This means if you execute an RTL, it will return to the location where it was armed.

Warning: In RTL mode the flight controller uses a barometer which measures air pressure as the 

primary means for determining altitude (“Pressure Altitude”) and if the air pressure is changing 

in your flight area, the copter will follow the air pressure change rather than actual altitude 

Auto Mode

In Auto mode the EH-4 will follow a pre-programmed mission script stored in the autopilot 

which is made up of navigation commands (i.e. waypoints) and “do” commands (i.e. commands 

that do not affect the location of the copter including triggering a camera shutter). 

AUTO mode incorporates the altitude control from AltHold mode and position control from 

Loiter mode and should not be attempted before these modes are flying well. All the same 

requirements apply including ensuring that vibration levels and compass interference levels are 

acceptable and that the GPS is functioning well including returning an HDOP of under 2.0.
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AUTO is programmed as a switch setting on a factory configured primary radio as shown in 

figure 8.

If starting the mission while the copter is on the ground the pilot should ensure the throttle is 

down, then switch to the Auto flight mode, then raise the throttle. The moment that the 

throttle is raised above zero, the copter will begin the mission.

If starting the mission from the air the mission will begin from the first command the moment 

that the switch is moved to Auto. If the first command in the mission is a take-off command 

but the vehicle is already above the take-off command’s altitude the take-off command will be 

considered completed and the vehicle will move onto the next waypoint.

At any time the pilot can retake control from the autopilot by returning the flight mode switch 

to another flight mode such as Stabilize or Loiter. If the pilot then switches to AUTO again, the 

mission will restart from the first command.

During the mission the pilot’s roll, pitch and throttle inputs are ignored but the yaw can be 

overridden with the yaw stick. This allows the pilot to for example aim the nose of the copter 

(which might have a hard mounted camera on it) as the copter flies the mission. The autopilot 

will attempt to retake yaw control as the vehicle passes the next waypoint.

Missions can be entered, amended through the Mission Planner’s Flight Plan screen. Please 

refer to the 3D Robotics Mission Command List wiki page for a full list of supported commands 

along with a short description of each.

Ending a Mission

Missions should normally have an RTL as their final command to ensure the copter will return 

after the mission completes. Alternatively the final command could be a LAND with a different 

location. Without a final RTL or LAND command the copter will simply stop at the final 

waypoint and the pilot will need to retake control with the transmitter.

Remember that when using RTL, the copter will return to the “home” position which is the 

location where the copter was armed.

As the copter touches down at the end of the mission the pilot should move the throttle to zero 

at which point the autopilot will disarm the motors if it also believes that it has landed.

Other AutoPilot flight modes may be configured by the PIC as mission parameters dictate:

Acro Mode

Acro - mode (Rate mode) uses the RC sticks to control the angular velocity of the copter. 

Release the sticks and the vehicle will maintain its current attitude and will not return to level. 

Acro mode is useful for aerobatics such as flips or rolls, or FPV when smooth and fast control is 

desired.
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Sport Mode

Sport -mode is also known as “rate controlled stabilize” plus Altitude Hold.

Drift Mode

Drift - Drift Mode allows the user to fly a multi-copter as if it were a plane with built in 

automatic coordinated turns.

Guided Mode

Guided - mode is a capability of APM: Copter to dynamically guide the copter to a target 

location wirelessly using a telemetry radio module and ground station application. This page 

provides instructions for using guided mode

Circle Mode

Circle- will orbit a point of interest with the nose of the vehicle pointed towards the center

Position Mode 

Position - is the same as loiter mode, but with manual throttle control. This means that, in 

position mode, the copter maintains a consistent location and heading, while allowing the 

operator to control the throttle manually.
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V. Flight Safety

Although sUAS are much safer than larger aircraft, and certainly safer than climbing and 

inspecting structures without the aid of any aircraft, it is still considered to be an aircraft and 

must always uphold the highest of safety procedures. This section will outline general safety 

measures to take with every mission. Additionally, an example checklist is provided to prepare 

and execute before every mission. This checklist is catered to the specific mission types of each 

client.

General Flight Safety Guidelines

The operation of any flying machine whether remote controlled or not can be dangerous. It is 

very important that you observe all necessary safety precautions before (and after) flying. A 

safety check list is provided at the end of this manual for your reference; please make sure you

use it. 

Spotters:

 Before a flight, the pilot must insure that the spotter understands his/her duties and 

expectations.

 A spotter should be used to assist in monitoring the surrounding airspace for 

manned aircraft whenever a flight is expected to exceed 400 feet above the ground 

and that operation is expected to be in proximity to known manned aircraft traffic

such as at a mixed-use facility or within three miles of an airport. 

 The spotter must have sufficient visual acuity and be mature enough to take this 

responsibility very seriously.

 A spotter should also be prepared to assist his/her pilot in the event that another 

model aircraft or spectators become endangered or in turn are perceived to be a

danger to the pilot or the pilot’s model aircraft.

Operating Parameters 

The operators must survey the area before any operation for obstructions, hazards, or anything 

unusual. No mission should be conducted unless a safe environment can be determined.
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General Preflight Checklist 

Physical Examination

Airframe for damage

Motor mounting for loose or missing hardware

Motor power leads for chaffing

Autopilot wiring for loose connectors or wire damage

Battery condition and charge level

Main Radio Connections

Other electrical/mechanical

On Site Safety Briefing

Site Survey

Selection of operating area and alternate

Crew Makeup

Crew Briefing

Space Safety Barrier

Communications

Weather Check

Refueling Procedure

Payload Installation and Operation

Failsafe procedures and operations

AP Calibration

Compass

Accelerometer/ Magnetometer

Radio (Yaw/Pitch/Roll/Throttle)

Modes

Fail Safe

Arm Aircraft

Battery Tone – good

Status Light – green
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Set Arm Button - on

Arm Tone 1 – good

Arm Tone 2 – good

Start Motors - Idle

Flight Checks

Manual launch and hover

Yaw Check

Pitch Check

Roll Check

Throttle Check

Begin Mission

End Mission

Dis Arm Aircraft

Set Arm Button - off

Disconnect and remove battery

Physical Inspection
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VI. Available Sensor Packages

A variety of sensor packages are available for attachment to the EH-4. All packages are 

mounted on an easy to remove cassette plate. Each sensor package contains its own 

independent power source. Currently available sensor packages are:

 GoPro Camera/Gimbal

 Garman Camera with GeoSpatial Tagging

 Forthwing ® NIR Agriculture Camera

 FLIR Tau Infrared Camera 

 Other custom payloads 

Sensor packages can utilize serial connections to the UAS, allowing the PIC to control some 

components of the sensors with telemetry or transmitter controls. Contact SelectTech 

GeoSpatial for additional operational and technical details for sensor and payload integration.

Figure 14 Sensor Cassettes available for the EH-4
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VII. Maintenance

Recommended Spare Components

Quantity Description

2 Motors, NeuMotor 725 RPM/Volt or equal

4 Propeller Sets, 11 x 5.5 (APC LP 11055 EP/E)

1 Landing Gear Set

1 Canopy/Cover

1 Airframe Set

1 Electronic Speed Control, Castle 35 Amp Quad

1 Spektrum AR8000 DSMX Receiver

10 10-32 x 3/8 Aluminum Socket Head Screws

10 10-32 x 3⁄4 long 1⁄4 Hex Aluminum Spacer

2 Batteries, LiPo 4S 14.8V 5600mAh 60C

4 M3x0.5 self-locking propeller nuts
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Aircraft Maintenance

Regular maintenance is required on a regular basis. The chart below indicates the major system 

areas that require maintenance attention.

In order to reduce propeller generated vibrations, a balance analysis needs to be completed on 

each propeller. Balancing needs to be completed upon initial installation, or after a hard landing 

that impacts the propellers. 

Aircraft/components 

(brief description) Manufacture Specification Inspection Maintenance Life limit

Airframe SGAMF G-10 Fiberglass/Resin Every Flight - Check for 

knicks/cracks

As inspection dictates Only if damaged

Powerplant NeuMotor 2015/8Y Kv: 742 RPM/Volt, Every Flight 10 Hours - Tighten 

Mounting Hardwary

One Year

Propellers

Advanced Precision 

Composites 11x5.5

Every Flight - Check for 

knicks/cracks As inspection dictates One Year

Electronic speed 

controller Castel Creations 35Quad 35 Amps

Every Flight - Check 

Connections As inspection dictates One Year

Batteries KYPOM 6200 mAh / 14 Volt

Check Connections, wire, 

plugs, Check for out 

gassing

As inspection dictates

3 months in 

continious use

Mechanical dynamic 

components

Landing Gear SGAMF Check for cracks As inspection dictates Unlimited Lifetime

Remote command and 

control I Spectrum DX-8

8 Channel Transmitter 

2.4 GHz Spred 

Spectrum

Check battery level every 

flight As inspection dictates Only if damaged

Remote command and 

control II 3-D Robotics 

Telemitry Tranciever 

915 MHz. Check RF connections As inspection dictates Only if damaged

Ground control station 3-D Robotics Mission Planner 1.3.5

Check RF and Signal 

Connections As inspection dictates Only if damaged

Autopilot APM Pixhawk Telemitry Tranciever 

915 MHz.

Check RF and Signal 

Connections

As inspection dictates Only if damaged
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Figure 15 Typical Propeller Balancer

Batteries and Safe Charging

The EH-4 uses Lithium Polymer rechargeable batteries as a power source. These 

batteries have been chosen for their high power density. 

Lithium Polymer Battery Safety (From National Renewable Energy Laboratory (NREL) :

Battery technology is at the heart of much of our technological revolution. One of the most 

prevalent rechargeable batteries in use today is the Lithium-ion battery. 

Although lithium-ion batteries are very common there are some inherent dangers when using 

ANY battery. Lithium cells are like any other technology – if they are abused and not used for 

their intended purpose catastrophic results may occur, such as: first-, second-, and third-degree 

burns, respiratory problems, fires, explosions, and even death. Please handle the lithium-ion 

batteries with care and respect. 

User Safety Precautions 

Short-Circuiting 

• When the battery is not in use, you MUST disconnect the battery from the battery connector. 

When the battery is connected to the battery connector, do not leave unattended since the 

two wires with the alligator clips can touch which will heat up the battery. Short circuiting will 

damage the battery and generate heat that can cause burns. 
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• Don't leave the battery in the charger once it is fully charged. The battery charger will flash on 

and off with a red indicator light every 20 seconds when the battery is fully charged. 

Overcharging the batteries will not increase the performance and could lead to damage. 

Disassembly 

• Never disassemble a battery as the materials inside may be toxic and may damage skin and 

clothes. 

• DO NOT place a battery in fire; this may cause the battery to rupture. The electrolyte is very 

flammable and if an ignition source exists, then fire and even an explosion could result.

NEVER place batteries in water, as this may cause the battery to rupture and release poisonous 

gasses. Furthermore, when the electrolyte is combined with water, there is the potential for 

hydrofluoric acid to form – an extremely toxic and corrosive substance.

Soldering 

• Never solder anything directly to a battery. This can destroy the safety features of the battery 

by damaging the safety vent inside the cap. 

Charging 

• Never charge with an unspecified charger or specified charger that has been modified. This 

can cause breakdown of the battery or swelling and rupturing. 

• Never attempt to charge a battery which has been physically damaged. 

• Avoid designing airtight battery compartments. In some cases, gases (oxygen, hydrogen) may 

be given off, and there is a danger of a battery bursting or rupturing if ignited by sparks. 

• Do not use a battery in an appliance or purpose for which it was not intended. 

Safety Procedures 

• If the foil packaging on the battery does break, vent the room and leave area. 

• If a fire starts, call the fire department immediately. The only extinguisher that will work on a 

Lithium-ion Battery fire is a Class D Fire Extinguisher or Dry Sand or Dry Table Salt. 

Battery Disposal 

Lithium-ion batteries are found in many electronics like laptops, digital cameras, power tools, 

and cordless phones. These batteries are very popular because they can be recharged and 

because they are able to supply power for a long period of time. However, even lithium-ion 

batteries reach a point where they can no longer hold a charge and need to be disposed of. 

When this time comes, it is important to know how to recycle the battery, and not simply put it 

in a trash can. Determine your states recycling policy. 
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There are many reasons to recycle these batteries rather than throw them away where they 

may end up in a regular landfill. 

Battery Maintenance

In order to maintain flight batteries in top condition, they should be continuously monitored. 

Prior to each flight and during the mission, the voltage should be checked. At no time should 

the voltage be allowed to go below 3.2 volts per cell. For safety reasons, landing voltages 

should be at 25% full charge (13.8 Volts). Flight voltages can be monitored via telemetry 

received at the ground station.

Figure 16 Battery Analyzer
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Figure 17 Battery Charger
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FAA statement on Unmanned Aircraft Systems(Reprinted From FAA Site)

Safety is the FAA's top mission, and the agency maintains the world's safest aviation system. 

The FAA first authorized use of unmanned aircraft in the National Airspace System (NAS) in 

1990.

Today, unmanned aircraft are flying in the NAS under very controlled conditions, performing 

border and port surveillance by the Department of Homeland Security, helping with scientific 

research and environmental monitoring by NASA and NOAA, supporting public safety by law 

enforcement agencies, helping state universities conduct research, and supporting various 

other missions for public (government) entities. Operations range from ground level to above 

50,000 feet, depending on the specific type of aircraft. However, UAS operations are currently 

not authorized in Class B airspace (PDF), which exists over major urban areas and contains the 

highest density of manned aircraft in the National Airspace System.

There are three types of unmanned aircraft system operations: Civil, Public and Model Aircraft.

 Civil UAS

Obtaining a Special Airworthiness Certificate in the experimental category for a particular UAS 

is currently the only way civil operators of unmanned aircraft are accessing the NAS. 

Experimental certificate regulations preclude carrying people or property for compensation or 

hire, but do allow operations for research and development, flight and sales demonstrations 

and crew training. The FAA is working with civilian operators to collect technical and 

operational data that will help refine the UAS airworthiness certification process. The agency is 

currently developing a future path for safe integration of civil UAS into the NAS as part of 

NextGen implementation. Read more about Civil Operations.

The FAA has been working for several months to implement the provisions of Section 333 of the 

FAA Modernization and Reform Act of 2012, "Special Rules for Certain Unmanned Aircraft 

Systems," which will allow for commercial operations in low-risk, controlled environments. 

Read more about Section 333.

 Public UAS

COAs are available to public entities that want to fly a UAS in civil airspace. Common uses today 

include law enforcement, firefighting, border patrol, disaster relief, search and rescue, military 

training, and other government operational missions. Applicants make their request through an 

online process and the FAA evaluates the proposed operation to see if it can be conducted 

safely. Read more about Public Operations.

 Model Aircraft
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Recreational use of airspace by model aircraft is covered by FAA Advisory Circular 91-57 (PDF), 

which generally limits operations for hobby and recreation to below 400 feet, away from 

airports and air traffic, and within sight of the operator. In June 2014, the FAA published a 

Federal Register notice (PDF) on its interpretation of the statutory special rules for model 

aircraft in the FAA Modernization and Reform Act of 2012. The law is clear that the FAA may 

take enforcement action against model aircraft operators who operate their aircraft in a 

manner that endangers the safety of the national airspace system. In the notice, the FAA 

explains that this enforcement authority is designed to protect users of the airspace as well as 

people and property on the ground. Read the full press release. Read more about Model 

Aircraft Operations.